Structure forming a lubricating layer on the surface thereof

ABSTRACT

A structure including a base material formed in a predetermined shape, and a lubricating layer formed on the surface of the base material for improving sliding property to a fluid substance, the lubricating layer comprising a liquid and solid particles. The lubricating layer  3  formed on the surface of the base material exhibits very improved sliding property to the fluid substance and enables the structure to be favorably used as a packing material such as container and lid.

TECHNICAL FIELD

This invention relates to a structure having a lubricating layer formed by using a liquid on the surface thereof. More specifically, the invention relates to a structure that exhibits improved sliding property to fluid substances due to the lubricating layer.

BACKGROUND ART

The containers for containing fluid contents must be capable of favorably discharging the contents irrespective of the materials forming the containers. Discharging the content is not almost of a problem when the liquids having low viscosity such as water and the like are contained. Discharging the content, however, becomes a serious problem when the content is a highly viscous substance such as mayonnaise or ketchup irrespective of the plastic container or the glass container. Namely, the contents of this kind are not quickly discharged despite the container is tilted. Besides, the contents tend to stay on the container wall and cannot be all recovered. Particularly, the content stays in considerable amounts on the bottom of the container and is not all recovered.

In recent years, there have been proposed various kinds of technical arts for improving sliding properties to viscous substances by forming a liquid film on the surface of a base material (e.g., see patent documents 1 and 2).

According to the above technical arts, the sliding property can be strikingly improved as compared to the cases of adding an additive such as lubricant to the synthetic resin that forms the surface of the base material, and attention has now been paid thereto.

Here, even according to means for improving surface properties by forming the liquid film on the surface of the base material as described above, it is not still possible to effectively prevent the content from adhering and remaining on the bottom of the container. Therefore, it has been desired to further improve the sliding property.

There has, further, been proposed a container with fine particles of a hydrophobic oxide adhered on the inner surface thereof and featuring excellent non-adhering property (patent document 3).

However, the sliding property expressed by the above container is very weaker than that expressed by the container provided with the liquid film.

Besides, improving the sliding property to the above-mentioned fluid substances has been desired not only for the containers but also for the lid materials and for the members such as pipes for flowing viscous fluid substances.

PRIOR ART DOCUMENTS Patent Documents

-   Patent document 1: WO2012/100099 -   Patent document 2: WO2013/022467

OUTLINE OF THE INVENTION Problems that the Invention is to Solve

It is, therefore, an object of the present invention to provide a structure having a lubricating layer on the surface thereof and exhibiting, due to the lubricating layer, further improved sliding property to fluid substances and, specifically, to viscous fluid substances.

Another object of the present invention is to provide a structure that exhibits further improved sliding property to the content and that can be favorably used as a packing material such as container and lid.

A further object of the present invention is to provide a container that exhibits sliding property to the content, the sliding property being improved to such an extent that a viscous content is effectively prevented from adhering or remaining on the bottom portion.

Means for Solving the Problems

According to the present invention, there is provided a structure including a base material formed in a predetermined shape, and a lubricating layer formed on the surface of the base material for improving sliding property to a fluid substance, the lubricating layer comprising a liquid and solid particles.

In the structure of the present invention, it is desired that:

(1) The liquid contained in the lubricating layer acquires an angle of contact (20° C.) of not more than 45° relative to the surface of the base material that supports the lubricating layer and has a viscosity (25° C.) of not more than 100 mPa·s; (2) The solid particles are organic particles; (3) The solid particles are present in the lubricating layer in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the liquid in the lubricating layer; (4) The lubricating layer is formed in an amount of 1.0 to 6.2 mg/cm² on the surface of the base material; (5) The surface of the base material is formed of a synthetic resin; and (6) The surface of the base material is formed of a glass.

It is further desired that:

(7) The structure is used as a packing material; (8) The packing material is used for containing a fluid content that has a viscosity (25° C.) of not less than 1260 mPa·s; and (9) The packing material is a container.

Effects of the Invention

Referring to FIG. 1, the structure of the present invention has a lubricating layer 3 formed on the surface of a base material 1 that comes in contact with a fluid substance, the lubricating layer 3 containing a liquid 5 and solid particles 7 (fine particles having a particle size of, for example, not more than 300 μm). That is, the fluid substance flowing on the surface of the base material 1 comes in contact with the lubricating layer 3 and, therefore, a greatly improved sliding property is exhibited to the fluid substance.

It has been known already that the sliding property to the content improves if a liquid layer is formed on the surface of a packing material such as container. If a viscous content is to be discharged from the packing material (e.g., container) having the above liquid layer formed on the inner surface thereof, then the content is discharged from the packing material in liquid-liquid contact. That is, the content flows down along the inner surface of the packing material not in solid-liquid contact but in liquid-liquid contact. Therefore, if an oily liquid is used that is immiscible with the content, then the sliding property can be improved to an aqueous substance that contains water. Further, if an aqueous fluid is used that is immiscible with the content, then the sliding property can be improved to an oily substance.

Here, the lubricating layer 3 possessed by the structure of the present invention includes two components, i.e., the liquid 5 and the solid particles 7. Therefore, a further improved slipping property is exhibited to the liquid substance (e.g., content in the container) than that of when the layer of liquid only is formed.

For example, as demonstrated in Experimental Examples appearing later, the slide-down velocities of the mayonnaise-like food are compared (for detailed conditions, refer to Examples) between the Experimental Example 18 (Comparative Example) in which the liquid layer of liquid paraffin (containing no solid particles) is formed on the surface of a polypropylene sheet and the Experimental Example 1 (Example of the invention) in which the lubricating layer containing the liquid paraffin and fine solid particles (rice wax) is formed on the polypropylene sheet. In this case, the mayonnaise-like food slides down more quickly in Experimental Example 1.

That is, both the liquid 5 (liquid paraffin) and the solid particles 7 (rice wax) work to improve sliding property to the fluid substances. In the present invention, further, due to the presence of the solid particles 7, the liquid 5 in the lubricating layer 3 is held on the surface of the base material 1. Due to the liquid 5, further, the solid particles 7 are also stably held on the surface of the base material 1. As a result, the sliding properties due to both of them are synergistically improved accounting for the expression of very excellent sliding property.

If used, specifically, as a container such as bottle, the structure of the present invention works to greatly suppress the content from adhering or remaining on the bottom portion in addition to exhibiting improved sliding property to the content.

For instance, in Tables 1 and 2 appearing later, the bottles filled with a mayonnaise-like food (viscosity: 1260 mPa·s@25° C.) as the content have been evaluated for the adhesion of food on the bottom portion. In the bottles in which the lubricating layer 3 containing the liquid 5 and the solid particles 7 is formed on the inner surface thereof according to the present invention, it is learned from the results of the tests that adhesion of the mayonnaise-like food has been greatly suppressed.

As for the reason why the content is effectively suppressed from adhering or remaining on the bottom portion, the present inventors consider that even after the content has slipped down, the solid particles 7 still remain on the surface of the base material 1 and hold the liquid 5 thereon. As a result, it is considered that the lubricating layer 3 containing the liquid 5 and the solid particles 7 is suppressed from being dissipated. That is, with the lubricating layer 3 being simply formed by using the liquid 5 only, if the container is inverted or is tilted, the liquid 5 splits away due to its own weight from the surface of the base material 1 (inner surface of the container). As a result, the sliding property to the content greatly decreases on the bottom portion. In the present invention, however, the solid particles 7 are made present in the lubricating layer 3. Therefore, the liquid 5 is firmly held on the surface of the base material 1 (inner surface of the container), and the sliding property is stably exhibited in the bottom portion, too.

Further, if the container which is the most preferred embodiment of the structure of the present invention is inverted or tilted to discharge the content out of the container, part of the liquid 5 and part of the solid particles 7 fall down and are discharged together with the content.

Here, however, the solid particles 7 holding the liquid 5 on the surfaces thereof slip down less than the content. If the container is returned back to the erected state, therefore, the solid particles 7 stay on the bottom portion of the container and work again to exhibit excellent sliding property when the content is discharged next time.

Upon selecting a suitable kind of the liquid 5 and a suitable kind of the solid particles 7, the structure or the container of the present invention can be favorably used for containing viscous contents that could not be smoothly discharged so far. Specifically, the structure of the present invention can be most favorably used as a container for containing the contents having viscosities (25° C.) of not less than 1260 mPa·s, such as mayonnaise, ketchup and a variety of kinds of dressings.

In the structure of the present invention described above, the lubricating layer 3 can be easily formed on the surface of the base material 1 (e.g., on the inner surface of a packing material) by applying, e.g., by spray means, a coating liquid comprising the liquid 5 and the solid particles 7 dispersed therein onto the surface of the base material 1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a model view illustrating the state of a lubricating layer formed on the surface of a structure of the present invention.

FIG. 2 is a model view illustrating the state of the solid particles present in the lubricating layer.

FIG. 3 is a view showing a directly blow-formed bottle which is a preferred embodiment of the structure of the present invention.

FIG. 4 is a view illustrating conditions for testing the sliding property.

MODES FOR CARRYING OUT THE INVENTION <Surface of the Structure>

Referring to FIG. 1, no particular limitation is imposed on the base material 1 having a surface that becomes the underlying layer of the lubricating layer 3 in the structure of the present invention if it is capable of holding the liquid 5 and the solid particles 7 contained in the lubricating layer 3 and, at the same time, if it can be formed to meet the mode of the packing material. Namely, the material may be a synthetic resin, a glass or a metal. That is, the structure of the present invention is favorably used as a packing material or as a pipe for flowing viscous fluid substances. Specifically, the packing material may be a synthetic resin container, a glass container, a metal container, or may be a lid made of a synthetic resin used for sealing the mouth portion of a container or may be a pouring fitting made of a synthetic resin used for pouring the content out of the container.

When the structure is used as a container, in particular, it is desired that the present invention is adopted to the base material 1 that is used as the container of which the inner surface is formed of a synthetic resin or glass and, specifically, of which the inner surface is formed of the synthetic resin that has heretofore been used for containing viscous contents. This is because the viscous content can be easily discharged. Therefore, the material forming the inner surface of the packing material (surface of the base material 1) is, most desirably, a synthetic resin.

The synthetic resin desirable as a material for forming the surface of the base material 1 (hereinafter called underlying resin) may be any thermoplastic resin or thermosetting resin that can be formed. Usually, however, a thermoplastic resin is preferred from such a standpoint that it can be easily formed and that it is capable of stably holding the oily liquid 5 and the solid particles 7 that hold the oily liquid 5 on the surfaces thereof.

As the thermoplastic resin, there can be exemplified the following resins; i.e.,

olefin resins such as low-density polyethylene, high-density polyethylene, polypropylene, poly(1-butene), poly(4-methyl-1-pentene), and random or block copolymers of α-olefins such as ethylene, propylene, 1-butene or 4-methyl-1-pentene, and cyclic olefin copolymers thereof;

ethylene.vinyl copolymers such as ethylene.vinyl acetate copolymer, ethylene.vinyl alcohol copolymer and ethylene.vinyl chloride copolymer;

styrene resins such as polystyrene, acrylonitrile. styrene copolymer, ABS and α-methylstyrene.styrene copolymer;

vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride.vinylidene chloride copolymer, poly(methyl acrylate) and poly(methyl methacrylate);

polyamide resins such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12;

polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate and copolymerized polyesters thereof;

polycarbonate resin;

polyphenylene oxide resin; and

biodegradable resins such as polylactic acid and the like.

As a matter of course, it is also allowable to use a blend of the above thermoplastic resins as the underlying resin so far as it does not impair the formability.

In the invention, among the above thermoplastic resins, it is desired to use an olefin resin and a polyester resin that have been used as materials of containers for containing viscous contents, and it is most desired to use the olefin resin.

That is, as compared to the polyester resin such as PET, the olefin resin has a low glass transition temperature (Tg) and shows a high molecular movement at room temperature. When the lubricating layer 3 containing an oily liquid such as edible oil is formed on the surface, therefore, the oily liquid (liquid 5) partly infiltrates into the interior of the olefin resin which, therefore, stably holds the lubricating layer 3 that contains the liquid 5 and the solid particles 7.

Besides, the olefin resin is highly flexible and is also used for directly blow-forming the squeeze-discharge containers (squeezable bottles). Therefore, the olefin resin is suitably used from the standpoint of adopting the invention to the containers of the above-mentioned type.

<Lubricating Layer 3>

As the liquid 5 used for forming the lubricating layer 3 on the surface 1 of the structure, a suitable liquid is used depending on the object (e.g., content in the packing material) to which the sliding property is exhibited by the surface 1. The liquid, as a matter of course, must be a nonvolatile liquid having a small vapor pressure under atmospheric pressure, such as a high-boiling liquid having a boiling point of not lower than 200° C. This is because if the volatile liquid is used, the liquid easily volatilizes and extinguishes with the passage of time making it difficult to form the lubricating layer 3.

Moreover, the liquid must have a high boiling point as described above and must, further, be immiscible with the fluid substance that flows on the surface of the base material 1. Further, the liquid must be highly wettable for the surface of the base material 1 and must be capable of forming the lubricating layer 3 evenly on the surface thereof. From these points of view, therefore, the liquid must acquire an angle of contact (20° C.) of, desirably, not more than 45 degrees with respect to the surface of the base material 1 and must have a viscosity (25° C.) of not more than 100 mPa·s. Namely, the lubricating layer 3 is formed by using the liquid 5 that satisfies the above-mentioned properties in combination with the solid particles 7 irrespective of if a synthetic resin, a glass or a metal is used as the material forming the surface of the base material 1.

Further, as for the liquid 5 that satisfies the above-mentioned properties, a liquid exhibits a high lubricating effect if it has a surface tension greatly different from that of the substance (e.g., content in the container) that is to slip down, and is suited for the present invention.

For example, to improve the sliding property to water or a hydrophilic substance that contains water, it is desired to use an oily liquid having a surface tension lying in a range of 10 to 40 mN/m and, specifically, 16 to 35 mN/m. Representative examples are liquid paraffin, synthetic paraffin, fluorine-contained liquid, fluorine-contained surfactant, silicone oil, fatty acid triglyceride and various plant oils. As the plant oils, there can be preferably used soy bean oil, rape oil, olive oil, rice oil, corn oil, safflower oil, sesame oil, palm oil, castor oil, avocado oil, coconut oil, almond oil, walnut oil, hazel oil and salad oil.

In the invention, further, it is desired that the lubricating layer 3 that contains the above-mentioned two components of the liquid 5 and the solid particles 7, is formed on the surface of the base material 1 (e.g., inner surface of the packing material) in an amount of 1.0 to 6.2 mg/cm². That is, if the amount thereof is too small or is too large, the lubricating layer 3 loses stability in exhibiting the effect for improving the sliding property.

In the invention, the solid particles 7 used as a component for constituting the lubricating layer 3 do not dissolve in the liquid 5 that is another component that constitutes the lubricating layer 3, are present therein in a solid form and do not, either, dissolve in a fluid substance (e.g., content in the container) that flows on the structure (on the surface of the base material 1). Here, it is desired that the solid particles 7 are fine particles having a particle size (median value of particles) of not more than 300 μm and, preferably, not more than 100 μm. If the particle size is too large, the particles impart less influence to the sliding property and, further, tend to easily split off due to their own weight. Therefore, the solid particles 7 fail to exhibit the effect of improving the sliding property to a sufficient degree. It is, further, desired that the particle size is not less than 5 μm from such a viewpoint that the particles are homogeneously dispersed in the structure 1 without being aggregated.

Further, the solid particles 7 must remain in a solid form when the lubricating layer 3 is being formed or when the structure is being used and, therefore, should have a melting point of which is not lower than 40 degrees.

There is no specific limitation on the material of the solid particles 7 which, therefore, may be formed by using any kind of organic material or inorganic material. From the standpoint of being held on the surface of the base material 1 and affinity to the liquid 5 that is the component constituting the lubricating layer 3, however, it is desired that the solid particles 7 are rather organic particles than such inorganic particles as metal particles or metal oxide particles.

Desirably, the particles are formed of, for example, olefin wax, rice wax, carnauba wax, various celluloses and cured organic resin (e.g., cured product obtained by curing a polyfunctional acrylic monomer). Specifically, the rice wax and the like are desired from such a standpoint that they can be used for the contents that are foods without limitation.

In the present invention, it is desired that the solid particles 7 are present in the lubricating layer 3 in an amount of 0.01 to 10 parts by mass and, specifically, 0.1 to 5 parts by mass per 100 parts by mass of the liquid that is the component constituting the lubricating layer 3 from such a standpoint that the solid particles are effectively held on the surface of the base material 1 while holding the liquid 5 on the surfaces thereof.

For instance, as shown in the model view of FIG. 2(a), if the amount of the solid particles 7 is too large, the solid particles 5 undergo the aggregation and fail to behave as apparently large particles, and exhibit decreased effect for improving the sliding property. Further, as shown in the model view of FIG. 2(b), if the amount of the solid particles 7 is too small, liquid 5 tends to split away and exhibits decreased effect for improving the sliding property. Specifically, if the structure is used as the container, the solid particles 7 fail to hold the liquid to a sufficient degree on the bottom portion. Therefore, the effect becomes insufficient for suppressing the adhesion or stay of the content on the bottom portion.

The solid particles 7 in the lubricating layer 3 may be exposed on the surface of the lubricating layer 3 in a state of holding the liquid 5. Or the solid particles 7 may at least partly be present being adhered to the surface of the base material 1. To produce the greatest effect for improving the sliding property, however, it is desired that most of the solid particles 7 have been dispersed in the lubricating layer 3.

In the invention, further, the lubricating layer 3 which contains the above-mentioned solid particles 7 can be easily formed on the surface of the base material 1 such as container by preparing a coating solution by mixing a predetermined amount of solid particles 7 in the liquid 5 that is the component constituting the lubricating layer 3 with stirring, and applying the coating solution by spraying or dipping. The lubricating layer 3 can also be formed by mixing a small amount of the liquid 5 and the solid particles 7 together, applying the resulting liquid 5 onto the surface of the base material 1 and, thereafter, spraying the remainder of the liquid 5 onto the layer that has been applied already.

<Form of the Structure>

There is no limitation on the form of the structure of the invention having the above-mentioned surface structure so far as the lubricating layer 3 containing the liquid 5 and the solid particles 7 is formed on the surface of the base material 1 so as to comes in contact with the fluid substance. Namely, the structure of the invention can be used in a variety of forms in which the base material 1 assumes a form that meets the use, such as in the form of pipe, container, lid and the like.

Specifically, the structure of the present invention is favorably adapted to the packing materials and in which the base material 1 favorably assumes the form of, for example, synthetic resin container, glass container, metal container, as well as lid and pouring fitting (spout).

Further, if the base material 1 forming the structure is a container having an inner surface made of a synthetic resin, the structure may be a single-layer structure with which the container as a whole is formed while using the synthetic resin to form the inner surface thereof, or may be a laminated-layer structure including layers of other synthetic resins.

Specifically, when the inner surface is formed of an olefin resin or a polyester resin, there can be employed the laminated layer structure including an oxygen-barrier layer or an oxygen-absorbing layer laminated via a suitable adhesive resin layer as an intermediate layer and, further, including, on the outer surface side, a layer of the same resin as the underlying resin (olefin resin or polyester resin) that is forming the inner surface.

The oxygen-barrier layer in the multi-layer structure is formed of an oxygen-barrier resin such as ethylene-vinyl alcohol copolymer or polyamide. The oxygen-barrier resin may be, further, blended with other thermoplastic resins in addition to the oxygen-barrier resin so far as the oxygen-barrier property is not impaired.

As described in JP-A-2002-240813 and the like, the oxygen-absorbing layer includes an oxidizable polymer and a transition metal catalyst. Due to the action of the transition metal catalyst, the oxidizable polymer is oxidized with oxygen; i.e., oxygen is absorbed and permeation of oxygen is shut off. The oxidizable polymer and the transition metal catalyst have been closely described in the above JP-A-2002-240813 and are not described here in detail. If described, however, representative examples of the oxidizable polymer are olefin resins having tertiary carbon atoms (e.g., polypropylene, polybutene-1, or copolymers thereof), thermoplastic polyester, aliphatic polyamide, xylene group-containing polyamide resin, and ethylenically unsaturated group-containing polymers (e.g., polymers derived from polyene, such as butadiene, etc.). As the transition metal catalyst, there can be exemplified inorganic salts of transition metals such as iron, cobalt, nickel, etc., organic acid salts thereof and complexes thereof.

Adhesive resins used for adhering the layers have been known per se., and examples thereof include olefin resins graft-modified with a carboxylic acid such as maleic acid, itaconic acid or fumaric acid or with an anhydride thereof, or with an amide or ester; ethylene-acrylic acid copolymer; ionically crosslinked olefin copolymer; and ethylene-vinyl acetate copolymer.

Thicknesses of the above layers may be suitably set depending on the properties required for the layers.

It is, further, allowable to provide, as an inner layer, a reground resin layer using a blend of a virgin resin such as olefin resin and scraps such as burr generated during the formation of the multi-layer structure (base material 1). For the container forming the inner surface (surface 1 of the above-mentioned structure) using the olefin resin or the polyester resin, further, it is also allowable, as a matter of course, to form an outer surface thereof using the polyester resin or the olefin resin.

There is no specific limitation on the shape of the container, either. Namely, the container may assume the form depending on the material for forming the container, such as cup, bottle, bag (pouch), syringe, pot, tray, etc., and may have been stretched.

Specifically, in the case of a synthetic resin container, a preform having the above-mentioned inner surface is formed by a method known per se., is subjected to the after-treatments such as sticking a film thereto by heat-sealing and vacuum forming such as plug assist forming or blow-forming to form a container. Further, as briefly described earlier, the coating solution obtained by dispersing the solid particles 7 in the liquid 5 that forms the lubricating layer 3 is sprayed onto the container to form the desired lubricating layer 3 that contains the solid particles. Depending on the form of the container, however, the coating solution is applied by using a roller or a knife coater to form the lubricating layer 3 on the inner surface of the container.

FIG. 3 shows a directly blow-formed bottle which is the most preferred embodiment of the structure of the present invention.

In FIG. 3, the bottle generally designated at 10 includes a neck portion 11 having a screw thread, a body wall 15 continuous to a neck portion 11 via a shoulder portion 13, and a bottom wall 17 that is closing the lower end of the body wall 15. The above-mentioned lubricating layer 3 is formed on the inner surface of the bottle 10 which is then filled with, for example, a viscous content.

The above-mentioned structure of the present invention exhibits very excellent sliding property depending on the kinds of the liquid 5 and the solid particles 7 that are the components constituting the lubricating layer 3, and exhibits the effect of preventing the content from adhering or staying on the bottom portion. Therefore, the structure of the invention can be favorably used, specifically, as a container for containing viscous contents having viscosities (25° C.) of not lower than 100 mPa·s. Specifically, if the liquid film 3 is formed by using the above-mentioned oily liquid, the structure of the invention is most desirably used as a bottle for containing viscous contents such as mayonnaise, ketchup, aqueous paste, honey, various sauces, mustard, dressing, jam, chocolate syrup, cosmetic such as milky lotion, liquid detergent, shampoo, rinse, etc.

EXAMPLES

The invention will now be described by way of the following Experimental Examples.

Described below are the container, lubricating liquid (liquid 5 which is the component constituting the lubricating layer 3) and contents used in Examples and in Comparative Examples.

<Container> (1) Sheet Members

As sheet members, there were used a multi-layer sheet of a width of 75 mm and a length of 50 mm cut out from a multi-layer bottle that will be described later, and a glass plate of a width of 75 mm and a length of 50 mm.

(2) Bottle

There was used a directly blow-formed multi-layer bottle having a multilayer structure of the following layer constitution and having a capacity of 400 g.

-   -   Inner layer: low-density polyethylene resin (LDPE)     -   Intermediate layer: ethylene-vinyl alcohol copolymer (EVOH)     -   Outer layer: low-density polyethylene resin (LDPE)     -   Adhesive layers (among the inner layer, intermediate layer and         outer layer): acid-modified polyolefin

<Lubricating Layer> (1) Liquid (Lubricating Liquid) for Forming the Lubricating Layer Edible Oil A:

-   -   Salad oil to which medium-chain fatty acid is added (viscosity:         33 mPa·s (25° C.), angle of contact: 18 degrees).

Edible Oil B:

-   -   Salad oil to which no medium-chain fatty acid is added         (viscosity: 80 mPa·s (25° C.), angle of contact: 18 degrees).

(2) Solid Particles

-   -   Rice wax.     -   Cellulose.

Coating solutions in which solid particles of specified particle sizes were dispersed were prepared by mixing solid particles into the above-mentioned liquids (lubricating liquids) shown in Tables 1 and 2 and stirring them together. The coating solutions were uniformly applied in specified amounts onto the sheet members of the containers and onto the inner surfaces of the bottles.

<Measurements> Particle Size of the Solid Particles;

Solid particles were mixed in an amount of 1% into the edible oil A, and the distribution of particle sizes was measured by the laser diffraction-light scattering method by using a particle size distribution measuring apparatus (LA-300 manufactured by: HORIBA, Ltd). A median value thereof was regarded to be a particle size.

Angle of Contact;

The inner surface of the container that is the multi-layer sheet of the sheet member was left to face upward, and 10 mg of an edible oil used as the lubricating liquid was dropped thereon. The angle of contact of the lubricating liquid was measured by using an instrument for measuring contact angles (DropMaster 700 manufactured by Kyowa Interface Science Co., Ltd.) at 20° C., 50% RH.

Viscosity;

A liquid was introduced into a beaker, and a spindle and a guard of a B-type digital viscometer were put into the liquid. While maintaining the temperature at 25° C., the spindle was turned at 10 rpm for one minute to measure the viscosity.

<Content>

An egg (50 g), 15 cc of vinegar and 2.5 cc of salt were mixed together and to which 150 cc of edible oil was, further, added to prepare a mayonnaise-like food for experiment. In Examples and Comparative Examples, the contents were prepared in required amounts and were used.

By using the contents of Experimental Examples, further, sliding properties (sliding properties of the sheet members) and sliding properties of the bottom portions (bottles) were evaluated in a manner as described below.

<Evaluating the Sliding Properties>

The coating solution was applied to the sheet member which was thereafter held at an angle of 30 degrees (see FIG. 4). 6 Milligrams of the mayonnaise-like food was dropped thereon, and the time was measured until it moved 5 cm. The sliding properties were evaluated on the following basis.

-   -   ⊚: Moved in less than 14 seconds.     -   ◯: Moved in not less than 14 seconds but less than 18 seconds.     -   Δ: Moved in not less than 18 seconds.     -   x: Not slipped down in not less than 60 seconds.

<Evaluating the Sliding Properties on the Bottom Portion of the Containers>

A spray nozzle was inserted in the bottle up to the bottom thereof and was pulled up while spraying the coating solution so that the coating solution was applied to the whole side wall surfaces starting from the bottom portion of the bottle. Into the bottle having the liquid film with the solid particles dispersed therein formed on the inner surface thereof, 400 g of the content or the mayonnaise-like food was introduced in a customary manner. The mouth portion of the bottle was heat-sealed with an aluminum foil and was sealed with a cap to obtain a filled bottle.

The bottle filled with the content was stored at 23° C. for one week. The bottle stored for one week was pressed on its body portion, and the content was squeezed out up to its last drip through the mouth portion of the bottle. Thereafter, the air was introduced into the bottle to restore its original shape.

Next, the bottle was inverted (mouth portion down) and was stored for one hour. Thereafter, the body wall of the bottle was measured in regard to what extent the content has slid down (to what extent the content has no longer been adhered to the body wall portion). The content slide-down ratio was calculated in compliance with the following formula.

Content slide-down ratio (%)=(surface area on which the content is sliding down/surface area of the body wall of the bottle)×100

From the content slide-down ratios calculated above, the sliding properties were evaluated on the following basis.

-   -   ◯: The content slide-down ratio is not less than 90%.     -   Δ: The content slide-down ratio is not less than 50% but is less         than 90%.     -   x: The content slide-down ratio is less than 50%.

Experimental Examples 1 to 6

By using the multi-layer sheet as the material for forming the inner surface of the packing material, coating solutions obtained by dispersing the rice wax (particle size of 100 μm) in the edible oil A (lubricating liquid) were applied thereon with the solid particle amounts and application amounts as shown in Table 1, and the sliding properties were evaluated.

Experimental Example 7

By using the multi-layer sheet as the material for forming the inner surface of the packing material, coating solution was applied thereon in the same manner as in Experimental Example 1 but changing the solid particles into the rice wax (particle size of 50 μm) with the solid particle amount and application amount as shown in Table 1, and the sliding property was evaluated.

Experimental Example 8

By using the multi-layer sheet as the material for forming the inner surface of the packing material, a coating solution was applied thereon in the same manner as in Experimental Example 1 but changing the solid particles into the rice wax (particle size of 250 μm) with the solid particle amount and application amount as shown in Table 1, and the sliding property was evaluated.

Experimental Example 9

By using the multi-layer sheet as the material for forming the inner surface of the packing material, a coating solution was applied thereon in the same manner as in Experimental Example 1 but changing the lubricating liquid into the edible oil B with the solid particle amount and application amount as shown in Table 1, and the sliding property was evaluated.

Experimental Example 10

By using the multi-layer sheet as the material for forming the inner surface of the packing material, a coating solution was applied thereon in the same manner as in Experimental Example 1 but changing the solid particles into the cellulose (particle size of 120 μm) with the solid particle amount and application amount as shown in Table 1, and the sliding property was evaluated.

Experimental Example 11

By using the glass plate as a material for forming the inner surface of the packing material, the coating solution was applied thereon in the same manner as in Experimental Example 1 with the solid particle amount and application amount as shown in Table 1, and the sliding property was evaluated.

Experimental Example 12

By using the multi-layer bottle as the packing material, a coating solution obtained by dispersing the rice wax (particle size of 100 μm) in the edible oil A was applied thereon with the solid particle amount and application amount as shown in Table 1, and the sliding property on the bottom portion was evaluated.

Experimental Example 13

By using the multi-layer bottle as the packing material, a coating solution obtained by dispersing the rice wax (particle size of 50 μm) in the edible oil A was applied thereon with the solid particle amount and application amount as shown in Table 1, and the sliding property on the bottom portion was evaluated.

Experimental Example 14

By using the multi-layer bottle as the packing material, a coating solution obtained by dispersing the rice wax (particle size of 250 μm) in the edible oil A was applied thereon with the solid particle amount and application amount as shown in Table 1, and the sliding property on the bottom portion was evaluated.

Experimental Examples 15 and 16

By using the multi-layer sheet as the material for forming the inner surface of the packing material, coating solutions obtained by dispersing the rice wax (particle size of 100 μm) in the edible oil A were applied thereon with the solid particle amounts and application amounts as shown in Table 2, and the sliding properties were evaluated.

Experimental Example 17

By using the multi-layer sheet as the material for forming the inner surface of the packing material, a coating solution obtained by dispersing the rice wax (particle size of 350 μm) in the edible oil A was applied thereon with the solid particle amount and application amount as shown in Table 2, and the sliding property was evaluated.

Experimental Example 18

By using the multi-layer sheet as the material for forming the inner surface of the packing material, the edible oil A was applied thereon in an amount as shown in Table 2, and the sliding property was evaluated.

Experimental Example 19

By using the multi-layer sheet as the material for forming the inner surface of the packing material, the rice wax applied thereon in an amount of 2.5 g and, thereafter, the edible oil A was applied thereon in an amount as shown in Table 2, and the sliding property was evaluated.

Experimental Example 20

By using the multi-layer sheet as the material for forming the inner surface of the packing material, the sliding property was evaluated but without applying the lubricating liquid.

Experimental Example 21

By using the multi-layer bottle as the packing material, the edible oil A was applied thereon, and the sliding property on the bottom portion was evaluated.

Experimental Example 22

By using the multi-layer bottle as the packing material, the sliding property on the bottom portion was evaluated but without applying the lubricating liquid.

Tables 1 and 2 show the results of evaluation in the above Experimental Examples.

In Tables 1 and 2, Ex. stands for Experimental Examples.

TABLE 1 Evaluation Coating solution Amount Sliding Lubricating applied Sliding property Base material liquid Solid particles (mg/cm²) *1 down on bottom Ex. 1 multi-layer sheet edible oil A *2 (*4, 100 μm) 2.4 3 ⊚ — Ex. 2 ↑ ↑ ↑ 1 3 ◯ — Ex. 3 ↑ ↑ ↑ 6.2 3 ◯ — Ex. 4 ↑ ↑ ↑ 2.4 0.01 ◯ — Ex. 5 ↑ ↑ ↑ 2.4 5 ⊚ — Ex. 6 ↑ ↑ ↑ 2.4 10 ◯ — Ex. 7 ↑ ↑ *2 (*4, 50 μm) 2.4 3 ◯ — Ex. 8 ↑ ↑ *2 (*4, 250 μm) 2.4 3 ◯ — Ex. 9 ↑ edible oil B *2 (*4, 100 μm) 2.4 3 ◯ — Ex. 10 ↑ edible oil A *3 (*4, 120 μm) 2.4 3 ◯ — Ex. 11 glass plate ↑ *2 (*4, 100 μm) 2.4 3 ◯ — Ex. 12 multilayer bottle ↑ ↑ 2.4 3 — ◯ Ex. 13 ↑ ↑ *2 (*4, 50 μm) 2.4 3 — ◯ Ex. 14 ↑ ↑ *2 (*4, 250 μm) 2.4 3 — ◯ *1: Amount of solid particles dispersed (g/100 g of liquid), *2: rice wax, *3: cellulose, *4: particle size

TABLE 2 Evaluation Coating solution Amount Sliding Lubricating Solid applied Sliding property Base material liquid particles (mg/cm²) *1 down on bottom Ex. 15 multi-layer sheet edible oil A *2 (*3, 100 μm) 10 3 Δ — Ex. 16 ↑ ↑ ↑ 2.4 20 Δ — Ex. 17 ↑ ↑ *2 (*3, 350 μm) 2.4 3 Δ — Ex. 18 ↑ ↑ — 2.4 — Δ — Ex. 19 ↑ edible oil A was applied 2.4 — Δ — after rice wax has adhered Ex. 20 ↑ — — — — x — Ex. 21 bottle edible oil A — 2.4 — — Δ Ex. 22 ↑ — — — — — x *1: Amount of solid particles dispersed (g/100 g of liquid), *2: rice wax, *3: particle size

Upon forming the lubricating layer containing the liquid and the solid particles on the inner surfaces of the sheet member and the bottle, improved sliding property is exhibited to the content. It will, therefore, be learned that the content slides down excellently.

Experimental Examples 23 to 26

In compliance with the above Experimental Examples, the coating solutions containing the solid particles (rice wax) and the liquid (edible oil) in amounts as shown in Table 3 were applied each in an amount of 0.6 cc onto the glass members (preparates) and were allowed to cover the whole surfaces thereof. Thereafter, the preparates were held vertically for 30 seconds and were returned to the horizontal state to measure the remaining ratios (%) of the coating solutions per the areas. The results were as shown in Table 3.

TABLE 3 Amount of solid particles Remaining ratio (g/100 g of liquid layer) (%) Ex. 23 0 2 Ex. 24 0.1 9 Ex. 25 1 39 Ex. 26 10 85

As will be obvious from Table 3, the higher the ratio of the solid particles in the lubricating layer, the higher the remaining ratio of the lubricating layer.

Though not shown in Table, if the ratio of the solid particles is too high in the lubricating layer, the solid particles may aggregate together and may hinder the content from sliding down or may infiltrate into the content. Therefore, the ratio thereof (corresponds to the amount of the solid particles per 100 g of the liquid) is, desirably, 0.01 to 10% and, specifically, 0.1 to 5%.

DESCRIPTION OF REFERENCE NUMERALS

-   1: base material -   3: lubricating layer -   5: liquid -   7: solid particles -   10: bottle -   11: neck portion -   13: shoulder portion -   15: body wall -   17: bottom wall 

1. A structure including a base material formed in a predetermined shape, and a lubricating layer formed on a surface of the base material for improving sliding property to a fluid substance, the lubricating layer comprising a liquid and solid particles.
 2. The structure according to claim 1, wherein the solid particles have a particle size of not larger than 300 μm.
 3. The structure according to claim 1, wherein the liquid contained in the lubricating layer acquires an angle of contact (20° C.) of not more than 45′ relative to the surface of the base material that supports the lubricating layer and has a viscosity (25° C.) of not more than 100 mPa·s.
 4. The structure according to claim 1, wherein the solid particles are organic particles.
 5. The structure according to claim 1, wherein the solid particles are present in the lubricating layer in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the liquid in the lubricating layer.
 6. The structure according to claim 1, wherein the lubricating layer is formed in the amount of 1.0 to 6.2 mg/cm² on the surface of the base material.
 7. The structure according to claim 1, wherein the surface of the base material is formed of a synthetic resin.
 8. The structure according to claim 1, wherein the surface of the base material is formed of a glass.
 9. The structure according to claim 1, wherein the structure is used as a packing material.
 10. The structure according to claim 9, wherein the packing material is used for containing a fluid content that has a viscosity (25° C.) of not less than 1260 mPa·s.
 11. The structure according to claim 10, wherein the packing material is a container. 